The right of priority under 35 U.S.C. xc2xa7119(a) is claimed based on German Patent Application No. 101 03 176.9, filed Jan. 22, 2001, the entire disclosure of which is hereby incorporated by reference.
The present invention relates to a method for introducing at least one flat-tube insertion slot into a header tube for a heat exchanger. In a first step of the method, a sawcut is made into the header tube for the respective flat-tube insertion slot and, during a subsequent second step, the flat-tube insertion slot is configured by means of a slot punch. The slot punch punches into the region of the sawcut. Such a method is, for example, suitable for introducing one or a plurality of flat-tube insertion slots into header tubes of an air-conditioning system heat exchanger, of the type employed in motor vehicles as evaporators or condensers and/or gas coolers.
In a method of this type that is described in the DE 44 42 040 A2, the sawcut is carried out as a sawn slot to a depth which is, on the one hand, greater than the tube wall thickness and, on the other hand, less than the tube radius of the header tube. As a result, at the level of the sawcut, the header tube has a circular cross-sectional shape extending above a semi-circular shape at the opening. During a subsequent punching step, the short side regions of the header-tube wall section bounding the sawcut are then enlarged and calibrated to the final slot length by means of a slot punch. In this procedure, provision is made for the length of the sawcut introduced transverse to the header-tube longitudinal axis to be selected to be at least smaller than the header-tube inner diameter by twice the wall thickness of the header tube, so that during the punching step, the end region of the slot walls is pressed outwardly to beyond the outer envelope of the header tube, and the slot length is larger than the header-tube inner diameter.
WO 98/51983 A1 also discloses a method for producing flat-tube insertion slots in a multi-chamber header tube. This method includes two sequential sawing steps. During a first step, a sawn slot is made over the whole of the desired insertion slot width and, in fact, deeper than the wall thickness of the header tube. Thus, the slot reaches the individual chambers or longitudinal ducts of the header tube but does not reach as far as the longitudinal central plane of the header tube. During the second sawing step, the sawn slot made during the first sawing step is then deepened over a smaller width so that shoulders or steps are formed in the web regions which separate the individual chambers. These shoulders or steps serve as stop surfaces for the flat tube to be inserted, with the result that connecting ducts between the chambers remain when the flat tube is inserted. The slot length is selected to be somewhat less than the effective inner header-tube width, i.e., less than the outer width of the header tube less twice the tube wall thickness.
It is the principal object of the invention to provide a novel method for producing one or a plurality of flat-tube insertion slots in a header tube, with advantageous slot contour and/or in an advantageous manner.
In accordance with one aspect of the present invention, there has been provided a method for forming at least one flat-tube insertion slot in a heat exchanger header tube suitable for use in an air-conditioning system, comprising: making a sawcut in the header tube, the sawcut having a first length and a first width; and configuring the flat-tube insertion slot by punching into the region of the sawcut with a slot punch, the slot punch having at least one of a larger width and larger length relative to the respective first width and first length of the sawcut, to thereby form a rimmed opening having a rim on at least a portion of its periphery extending into the interior of the header tube.
In accordance with another aspect of the invention, there is provided a method for forming at least one flat-tube insertion slot in a heat exchanger header tube suitable for use in an air-conditioning system, comprising: making a sawcut in the header tube wherein the sawcut is introduced to a depth (d1) which is less than the wall thickness (D) of the header tube; and configuring the flat-tube insertion slot by punching into the region of the sawcut with a slot punch.
In accordance with still another aspect of the invention, there is provided a method for forming at least one flat-tube insertion slot in a heat exchanger header tube suitable for use in an air-conditioning system, comprising: making a sawcut in the header tube; and configuring the flat-tube insertion slot by punching into the region of the sawcut with a slot punch, wherein the header tube comprises a multi-chamber header tube having a plurality of adjacent tube passageways separated at a distance from one another by means of respective web region(s), and the flat-tube insertion slot extends transversely over a plurality of the tube passageways, and wherein during the punching, at least a portion of the respective web region(s) is compressed to a level lower than a flat-tube insertion stop, whereby a space connecting at least two of the passageways will be defined upon insertion of a flat tube.
Further objects, features and advantages of the present invention will become apparent from the detailed description of preferred embodiments that follows, when considered together with the accompanying figures of drawing.